Vascular access is important for the treatment of some chronic diseases such as those requiring hemodialysis treatments. A vascular access site should be prepared before starting those kinds of treatments because doing this allows for easier removal and replacement of the patient's blood during treatment. The access site should allow for continuous, high blood flow volumes. Common complications from vascular access sites include infection and low blood flow because the access passageway has clotted.
Arteriovenous (AV) fistulas or AV shunts are basic kinds of vascular access for hemodialysis. An AV fistula connects an artery to a vein in a patient (such as in the patient's forearm) and is useful because it causes the vein to grow larger and stronger allowing easier access to the blood system. The AV fistula is considered the best long-term vascular access for hemodialysis because it provides adequate blood flow, lasts a long time, and has a lower complication rate than other types of access. If an AV fistula cannot be created, an AV shunt or venous catheter may be needed.
An AV fistula requires planning because it takes time after surgery to develop—usually several months. But properly formed fistulas are less likely to form clots or become infected than are other access methods. Also, properly formed fistulas may work longer than other kinds of access—sometimes for years.
A synthetic arteriovenous shunt is another type of vascular access is. It connects an artery to a vein using a synthetic tube, or shunt, implanted in the patient's forearm, for example. The shunt becomes an artificial vein that can repeatedly receive a needle for blood access during hemodialysis. A shunt can be used sooner, 2 or 3 weeks after placement, than an AV fistula.
Compared with properly formed fistulas, shunts have more clotting and infection problems and need more frequent replacement.
Both types of access typically fail by clotting, which almost always starts with hyperplasia of the vessel wall near the venous anastomosis. What is needed is a convenient way to deliver a drug to that region without interfering with the function of the vascular access.